Action Points

Note that this study was published as an abstract and presented at a conference. These data and conclusions should be considered to be preliminary until published in a peer-reviewed journal.

On-demand pre-exposure prophylaxis with tenofovirdisoproxilfumarate/emricitabine (TDF/FTC) remained highly effective in men who have sex with men (MSM) who have infrequent sexual intercourse.

Note that the study was a post hoc analysis and there may be confounders, although a clinical trial might be difficult to conduct given this scenario of infrequent sexual activity.

PARIS – On-demand pre-exposure prophylaxis with tenofovir disoproxil fumarate/emtricitabine (TDF/FTC) remained highly effective in men who have sex with men (MSM) who have infrequent sexual intercourse, according to a sub-analysis of the ANRS IPERGAY study.

The incident infection rate among individuals who were not on pre-exposure prophylaxis (PrEP) was 9.3 per 100 person-years -- six infections over 64.8 person-years of follow-up -- versus 0 per 100 person-years among men using PrEP – based on 68.9 person-years (P=0.013), said Jean-Michel Molina, MD, of the Hôpital Saint Louis/University of Paris, and colleagues.

The ANRS IPERGAY study showed that among MSM, there was a 86% relative reduction of HIV1 incidence with on-demand PrEP in the TDF/FTC arm for an incidence of 0.91 per 100 person-years (two infections at 219 person-years of follow-up) versus 14 infections for an incidence of 6.60 per 100 person years (212 person-years of follow-up ) for placebo. Participants in this trial used a median of 15 pills per month and had a median of 10 sexual intercourse encounters month.

The post hoc analysis was performed in response to questions asked of researchers about what happened to IPERGAY study participants who used less than 15 tablets a month – that is, men who had infrequent sexual encounters with other men, Molina said at an International AIDS Society (IAS) Conference on HIV Science press conference.

"In Europe, PrEP is available as a daily treatment and on-demand by men who have sex with men," he explained. "The data have so far been limited by the double-blind study, but many of our investigators have been asked whether men who have infrequent sex are protected when they use on-demand PrEP. I think our data are a nice compliment to what has been presented previously."

"We restricted out analysis to people who took fewer than the median number of pills than in the trial. In the trial, the median number was 15 per month among those in the on-demand regimen. In restricting the subgroup to only those who used the pills when they had sex, in this group, the median number of sexual encounters a month was five, and 25% of that group had less than two encounters a month," he added.

The median number of pills used by the participants in the subgroup was 9.5 per month. "In these cases, the efficacy was very high ... this again adds to the evidence that on-demand PrEP is effective even in those men having less frequent sex," he said.

For the trial, Molina's group assumed that participants with less frequent sexual intercourse would use fewer pills. Because individual patterns of pill use showed large intra-participant variability over time, the researchers focused the analysis on person-time between two consecutive visits when participants used 15 or less pills /month and PrEP was used "systematically or often" during sexual intercourse, and not "from time to time or never."

They also also calculated the infection rate when condomless sexual acts were performed. That rate was 12.3/100 person-years in the placebo arm and 0/100 person-years in the patients treated with tenofovir/emtricitabine (Truvada, P=0.011).

A fourth generation HIV-1/2 ELISA assay was performed at each visit allowing to date the time of HIV-infection, Molina said.

"I think that with this study, with the pharmacokinetic study in humans and in animal studies, we have enough evidence to say that it is safe for men who have infrequent sex to use PrEP on demand," Molina told MedPage Today.

"The data is mounting on use of PrEP in this group of men who have sex with men. It will be interesting to see if the guideline feel this evidence is sufficient to recommend its use." commented IAS session moderator Linda-Gail Bekker, MBChB, PhD, IAS president and professor of medicine at the University of Cape Town. "If we are right about this, then it is a really valuable contribution to the toolbox."

But she also pointed out that the study was a "post hoc analysis and there may be confounders. Ad hoc analyses always make us nervous." However, she acknowledged that "a clinical trial might be difficult to conduct given this scenario of infrequent sexual activity."

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